Cable extensor and cable overload release unit



June 21, 1955 G M. 0115 2,710,974

CABLE EXTENSOR AND CABLE OVERLOAD RELEASE UNIT Fil'ed Dec. 6, 1952 2 Sheets-Sheet l [N V EN TOR G11. 8527' M Ma 7-1.5

Juana G. M. MOTIS June 21, 1955 CABLE EXTENSOR AND CABLE OVERLOAD RELEASE UNIT 2 Sheets-Sheet 2 Filed Dec. 6, 1952 l 97 ca' 114 INVENTOR 611.5527 M Mgr/s Milo/fig United States Patent CABLE EXTENSOR AND CABLE OVERLOAD RELEASE UNIT Gilbert M. Mods, Northridge, Califi, assignor to Northrop Aircraft, Inc, Hawthorne, Calif, a corporation of California Application December 6, 1952, Serial N 0. 324,536

1 Claim. (Cl. 3-12.6)

The present invention relates to artificial arms, and

more particularly to the mechanism for operating a terminal device such as a hook or hand.

In the majority of cases, the terminal device is actuated by a control cable of the type known as Bowden cable, wherein a flexible wire is slidably enclosed for the greater part of its length within a tubular conduit, and the latter is anchored near its ends to the artificial arm. The flexible wire is attached at one end to a shoulder harness or the like, and at the other end to an operating lever or bell crank on the terminal device. A shrug of the barnessed shoulder exerts a pull on the cable, causing the hook or hand to open or close against the tension of a spring, as the case may be.

Where the terminal device is provided with wrist fiexion and extension movement, and the control cable passes to one side of the fiexion-extension axis, any angular movement of the terminal device about the said axis has the effect of moving the outer end of the operating lever toward or away from the anchored end of the conduit. This necessitates shortening or lengthening the control cable in order to accommodate its length to the new position of the operating lever, and heretofore such adjustment has been made by means of telescoping or ratchet devices that were manually adjusted by the other hand. The chief disadvantage of such devices has been that they are difficult to operate with the other hand, particularly in the case of bilateral amputees. Another objection to the prior devices has been that their mode of operation necessitates locating the unit where it will be readily accessible to the other hand, which means that the device was necessarily exposed, and therefore vulnerable to damage.

One of the primary objects of the invention, therefore, is to provide a device for lengthening or shortening the control cable, which can be operated without requiring the use of the other hand. Another object is to provide a device of this type which can be located in any sheltered portion of the arm, where it will be protected from damage. Still a further object of the invention is to provide a device of the character described which can be operated by merely pressing a control means on the arm against the body or other object, and which functions automatically to take up any slack in the cable when thus operated.

A second aspect of the invention has to do with the provision of a cable overload release unit. This overload release function is obtained by a relatively slight modification of the mechanism, whereby the control cable itself trips the release when the tension stress therein exceeds a predetermined value. The purpose of the overload release mechanism is to protect the terminal device from damage, and the need for such a device has been accentuated by the substitution of steel cables for the previously used leather thongs or fiber cords. Leather thongs and fiber cords were self-limiting as to the maximum tension load that could be applied to the terminal device, owing to the fact that they would either stretch or break when overloaded, but the new steel cables are so much stronger than their predecessors that it has become possible for terminal devices to be damaged by shock loads or other excessive stresses. Another important object of the invention, therefore, is to provide a mechanism which will permit the cable to slip or elongate under excessive loads, so that the terminal device will be protected against overloads and saved from damage.

A further object is to provide an overload release mechanism which restores itself automatically to its normal operating condition as soon as the terminal device is unloaded, and which requires no attention on the part of the amputee to reset it.

The foregoing objects for both aspects of the invention are achieved by the provision of a small, compact unit which is serially connected into the control system, preferably between the shoulder harness and the Bowden cable. The cable is wrapped around a reel in the unit, which is spring loaded to wind up the cable thereon. A pivoted, spring-pressed locking lever engages a tooth in a notch on the periphery of the reel, thereby locking the reel against turning and preventing the cable from being unwound therefrom. As long as the reel is thus locked, the unit functions as a rigid, unyielding part of the control system, and the terminal device is operated each time that the cable is pulled by a shoulder shrug on the harness.

In the case of the cable extensor unit, the locking lever is disengaged from its seat in the reel by means of a manual control, which may take any of several forms but is herein represented by a push-pull cable of the type commonly used in cameras for operating the shutter release. The push-pull cable is operatively connected to apressure-operated control means on the arm, and when the said means is pressed against the body, the said cable is pushed or pulled to lift the locking lever out of its seat in the reel. As the reel is released, the spring rotates it in the direction to wind up any slack cable thereon. The reel is provided on its periphery with several notches which are spaced circumferentially to provide several length adjustments of the cable, and the locking lever drops into the notch that is closest to the desired position, relocking the reel for normal operation.

In the case of the cable overload release unit, the cable is drawn over a surface of the locking lever which is so located with respect to the pivot that a tension. force in the cable causes a thrust to be exerted on the lever opposite to the pressure of the spring, which urges the lever into seating engagement with the reel. When this unseatiug force exceeds the pressure of the said spring, the locking lever is lifted out of its seat, and the reel is released to turn. The excessive tension load on the cable causes it to unwind from the reel against the pressure of the torsion spring acting on the reel, until the terminal device is unloaded. Release of the tension in the cable by unloading of the terminal device allows the reel to rewind the cable thereon, and as the notch in the periphery of the reel moves into place beneath the locking lever tooth, the latter drops into its seat, locking the unit in its original condition in readiness for normal operation.

Further objects and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of two illustrative embodiments thereof, reference being had to the accompanying drawings, wherein:

Figure l is a perspective view of a typical artificial arm, showing one of the units of our invention connected into the control system thereof;

Figure 2 is a sectional view through the cable extensor form of our invention, showing the mechanism in the normal locked condition;

Figure 3 is a view similar to Figure 2, showing the mechanism in the unlocked condition, as when making an adjustment in length of the control cable system;

Figure 4 is a sectional view through the pressure operated control means, which functions to unlock the unit when pressed against the amputees body or other object;

Figure 5 is an elevational view, with cover plate removed, of the cable overload release form of our invention, showing the mechanism in the normal operating condition;

Figure 6 is a view similar to Figure 5, showing the mechanism in the released condition, as when the control cable has been overloaded; and

Figure 7 is a sectional view, taken at 7-7 in Figure 5.

The first form of my invention to be described will be the cable extensor embodiment illustrated in Figures 1 to 4, inclusive, which is designated in its entirety by the reference numeral 10. The artificial arm with which it is shown is of the above-elbow type, comprising an upper arm portion 11 and a lower arm portion 12, which are connected together for relative swinging movement by an elbow unit 13. Mounted on the distal end of the lower arm portion 12 is a wrist unit 14 and hook 15. The hook is swiveled on the Wrist unit for swinging movement about a pivot shaft 16 between the straight-out position shown in the drawing, the fully flexed position indicated at A, and the fully extended position indicated at B. Suitable locking means (not shown) is provided for locking the hook in any one of the three positions.

The hook is of the normally closed type and comprises a stationary finger 20 and movable finger 21; the latter being pivoted for swinging movement about a pivot bolt 22. Rubber bands 23 bind the fingers 20, 21 together, and the hook is pulled open against the tension of the rubber bands by means of a Bowden cable control wire 24. The wire 24 is attached to the outer end of a laterally projecting thumb 25 which is integral with finger 21, and passes through a length of springwound conduit 26 which is attached by a leather loop 30 to the forearm portion 12 adjacent the elbow. Further up on the arm, the wire 24 passes through another length of spring-wound conduit 31 which is attached to the upper arm portion 11 by an anchor fitting 32. The cable extensor unit 10 is attached to the upper end of the wire 24, and is attached, in turn, to one of the straps 33 of the usual shoulder harness.

Another Bowden cable control wire 34 passes through a spring-wound conduit 35 that is secured to the upper arm portion 11 by an anchor fitting 36. A yoke is attached to the upper end of the wire 34, and secured to the yoke is another strap 41 of the shoulder harness. The lower end of the wire 34 extends into the interior of the upper arm portion 11 through a hole 42, and is attached in any suitable manner to the lower arm portion 12, whereby the latter can be lifted by exerting a pull on the wire. Thus, a shoulder shrug in one direction exerts a pull on wire 34 to lift the forearm 12, while a shrug in another direction exerts a pull on control wire.

24 to open the hook 15.

Both the upper arm portion 11 and lower arm portion 12 are preferably, although not necessarily, formed of fabric-reinforced plastic shell construction, which produces a light-weight arm of great strength and durability. D-rings 43 are attached by straps 44 to the inner and outer sides of the upper arm portion 11, and straps (not shown) of the harness pass through the D-rings to hold the arm on the stump.

As shown in Figures 2 and 3, the cable extensor unit 10 comprises a relatively flat, generally rectangular casing 45 having an elongated slot 46 adjacent one end thereof, through which the harness loop 33 is passed. Formed in the casing 45 on one side thereof is a circular cavity 50, and nested within this cavity is a freely rotatable wheel, or pulley 51. A deep circumferential groove 52 is formed in the outer periphery of the pulley 51, and wrapped around the pulley at the bottom of said groove is a cable 53. One end of the cable 53 is soldered at 54 to the pulley 51, while the other end passes out of the casing through holes 55 and 56, and is joined by a connector to the upper end of control wire 24.

At the center of the pulley 51 is a circular opening 63, within which is disposed at spirally coiled clock spring 62. One end of the spring 62 is bent radially outward and inserted into a slot 63 in the pulley, while the other end thereof is secured by a lock pin 64 to a stationary hub 65. The hub 65 is fixed to the casing 45 at the center of the circular cavity fill, and the spring 62 is thus anchored at its inner end to the casing. In assem- 2 bling the unit, the spring 62 is wound up a few turns so as to exert a firm clockwise torque on the pulley 51, tending to wind the cable 53 thereon.

Also formed in the casing 45 parallel to the adjacent sides thereof is a generally L-shaped cavity 66 which opens at 70 into the circular cavity 50. A locking lever, or latch 71 occupies one leg of the cavity 66 and is pivoted on a tubular shaft 72 for limited swinging movement. The lower end portion of the locking lever is slotted at 73 to provice an open passageway through which the cable 53 passes, and the side portions on either side of the slot are provided with lateral projections which reach through the opening 70 to form teeth 74. The teeth 74 are engageable in any one of three sets of notches 75 formed in the flanges of the pulley 51, and when the teeth are seated in the said notches the pulley is locked against rotation.

A spring '76, occupying the bottom leg of cavity 66 and anchored at one end to a tubular rivet 77, is hooked at the other end over a transverse pin 78, which is fixed to the bottom end of the locking lever and bridges the slot 73. The spring 76 exerts a clockwise pressure on the locking lever, urging the teeth 74 into seating engagement in their notches 75. From this it will be seen that the unit is normally in the locked condition, and the pulley is rigidly held against rotation in either direction. As long as the pulley is thus locked, the unit functions as a rigid, unyielding part of the control system, and the terminal device is operated each time that the cable is pulled by a shoulder shrug on the harness.

Disengagernent of the locking lever 71 from the pulley 51 to efiect adjustment in the overall length of the control cable is accomplished through the agency of a pressure-operated control means 80 mounted on the side of the forearm member 11 adjacent the amputees body. The control means 80 may take other forms, but for purposes of illustration is herein shown as comprising an outwardly facing, cup-shaped body 81 which is riveted to the forearm shell.

Disposed within the body 81 and attached at one end to the adjacent end of the body is an arched leaf spring 82, the free end of which has a transversely extending pin 83 soldered thereto. The projecting ends of pin 83 are slidably disposed within slots 84 in opposite sides of the body 81, and when the spring is pressed down fiat, the free end thereof moves to the left, as viewed in Figure 4, sliding the pin 83 along the slot. One end of a push-pull control wire 85 is attached to the free end of the spring 82, and when the spring end moves to the left, the control wire 85 is pushed ahead of it.

The control wire 85 extends through a flexible tube 86 up to the unit 10, and terminates in a plunger 90, which abuts against the side of an extension 91 on the locking lever 71 at the upper end thereof. Fittings 92 and 93 at the ends of the tube 86 are connected into the body 81 and casing 45, respectively. A dome-shaped rubber cap 94 having a boss 95 projecting from the center thereof is fitted to the body 81 to enclose and protect the spring 82.

When it becomes necessary to increase the length of the control cable, as when the hook 15 is swung out to a more extended position (such as, for example, from the position shown in Figure 1 out to position B) the amputee needs only to press the upper arm 11 in against his body, thereby depressing the boss 95 and flattening the arched spring 82. This causes the control wire 85 and plunger 90 to push the locking lever over to the position shown in Figure 3, lifting the teeth 74 out of the notches 75 in the pulley flanges. The hook 15 can then be swung out to position B, unwinding the necessary extra length of control cable from the pulley 51 against the tension of the spring 62 and bringing the next set of notches 75 into position to be engaged by the teeth 74 when the pressure on the control means 80 is released.

When it is desired to take up excessive slack in the control cable, as when the hook 15 has been swung in to a more flexed position (for example, to position A) pressure is applied to the control means 80, disengaging the locking lever 71 from the pulley 51 and allowing the spring'62 to rotate the pulley in a clockwise direction to take up the slack in the cable. Again, when pressure on the control means 80 is released, the teeth 74 on the locking lever drop into whichever notches 75 are now in position to be engaged.

In the event that the rotational movement of the pul ley 51 carries the notches 55 somewhat past the locking lever teeth 74, release of pressure on the control means 80 will merely cause the teeth to drop against the outer periphery of the pulley flanges. In this condition the pulley is not locked, and the first application of tension to the control system causes the pulley to unwind until the notches move around into position to be engaged by the locking lever teeth.

The internal mechanism of the unit is enclosed by a protective cover plate, such as that shown at 98 in Figure 7, which is secured to the outer face of the casing 45. To this end, a shallow transverse recess 96 is milled into the casing, leaving undercut side flanges 97 along opposite ends thereof. The cover plate is provided with beveled edges which dovetail into the undercut flanges when the plate is slipped endwise into the recess, thereby holding the plate to the casing. The ends of the tubular members 77 and 72 project through holes in the bottom of the casing and in the cover plate, and these ends are peened down to rivet the cover plate to the casing.

The cable overload release of the mechanism will now be described, and for the description that follows, reference is had to Figures 5, 6 and 7. Parts that are substantially identical to those already described are given the same reference numeral with the prime suffix. The casing 45 is generally similar to the one previously described, and is provided with a circular cavity 53, within which is disposed a freely rotatable pulley, or wheel 51'. The channel 52' in the periphery of the pulley is somewhat wider than in the first embodiment, and the cable 53 is wrapped twice around the pulley. It will be noted that there is only one set of notches '75 in the pulley flanges, and the locking lever tooth 74' is somewhat diflerent in shape from the preceding model, for reasons which will be explained more fully hereinafter.

Upon leaving the pulley channel, the cable 53 slides over a curved ramp or bearing surface 100 that is milled in the locking lever 71 from one side thereof, which changes the direction of the cable and puts a substantial bend therein. Under tension, cable 53 attempts to straighten out this bend, but is prevented from doing so by the ramp 160. The result is that the cable exerts a thrust force against the locking lever proportional to the tension and substantially in the direction of the arrow F. It will be noted that the arrow F is directed downwardly and to the right, and passes well to one side of the pivot center of the locking lever. The thrust force F thus acts along a moment arm M to exert a clockwise out of its socket 75, against the pressure of spring '76.

Spring 76' diifers slightly from its counterpart in the first embodiment in appearance and in certain other respects, being a compression spring instead of a tension spring, and pressing the top end of the locking lever 71' to the left, instead of pulling the bottom end to the left, as in Figure 2. However, the function of spring 76' is the same as in its counterpart; the purpose being to exert a yielding pressure against the locking lever in the direction to hold the tooth 74' in seating engagement with the notch 75'. Another structural difference which might be noted at this point is the tension-adjusting screw 101, the head of which provides a footing for the right hand end of the spring 76'. Screw 101 passes through the center of spring 76' and through an oversized hole 102 in the top end of the locking lever, and screws into a tapped hole 103 in the casing. The head of the screw 101 passes freely through a hole 104 in the end of the casing, and is normally positioned within the hole, as shown in Figure 5. The pressure exerted by the spring against the locking lever 71 can be regulated by turning the screw 101 in, or backing it out of the tapped hole 103, thereby compressing the spring to a greater extent or releasing the pressure, as the case may be.

The underneath side of locking tooth 74 and the corresponding surface of notches 75' are cut back and up at a slight angle to the arcuate pathfollowed by the tooth when the locking lever is swung in a clockwise direction, which causes the tooth to cam the pulley slightly in a clockwise direction, in opposition to the counterclockwise pull of the cable 53', when the locking lever is pulled away from the pulley. The cam angle is relatively small, but its effect is suflicient to prevent the tooth from slipping out of its notch under normal operating loads.

In order to prevent the tooth 74 from dropping into the notch 75' when the wheel has made just one revolution, an interference plate is provided, which is disposed between the wheel and the bottom of the cavity 50. The plate 110 is preferably in the form of a flat ring of the same outside diameter as the wheel, and is rotatable with respect to both the casing 45' and the wheel 51'. A square notch 111 that is somewhat larger than notch 75' is provided in the outer edge of the plate 110, and when the unit is in operating condition, as in Figure 5, the two notches line up with one another. The tooth 74 is wide enough to bear on both the wheel 51' and plate 110, and therefore can enter notch 74 in the wheel only when notch 111 is alined therewith. Whenever the plate is rotated to a different position, as in Figure 6, wherein the notch 111 is located where it cannot receive the tooth 74', the latter merely comes down on the outer periphery of the plate and is held thereby against dropping into notch 75 in the wheel.

A tab 112 projects radially inward from the inner edge of the ring, and is engageable by one side of a stop 113, to position the notch 111 in line with notch 75'. The stop 113 comprises one ear projecting from one side of the hub 65 in the plane of the plate 110, the ear being riveted at 114 to the bottom of the casing. This arrangement secures the stop solidly to the casing, and also locks the hub 65 against turning under the torsional force of the spring 62'.

In normal operation, the mechanism of the unit is as shown in Figure 5, with the wheel 51 locked against rotation by the locking lever 71. In this condition, the unit functions as a rigid, unyielding part of the control system, and the terminal device is operated each time that a pull is exerted on the strap 33. The spring 76' holds the tooth 74 in the notch 75' against the unseating force exerted by the cable 53 at F for all normal loads. If an excessive load is placed on the control system, however, the force at F overcomes the spring 76, and the tooth 74 is lifted out of the notch 75, releasing the Wheel. The wheel then rotates in a counterclockwise direction,

paying out cable to release the load thereon. As the wheel rotates, frictional drag on the plate 110 causes the latter to be carried around with it until the tab strikes the other side of the stop 113, as shown in Figure 6. This the tooth 74', so that the tooth is prevented from dropping into the notch 75 the next time that the latter passes under the tooth. The wheel is thus allowed to rotate until suflicient cable 53' has been paid out to insure full release of the overload in the control system.

Upon release of the load, the wheel 51 is rotated back in a clockwise direction by the spring 62, winding the cable back onto it. The plate 110 is again dragged along with the wheel until the tab 112 engages the first side of the stop 113, whereupon the plate stops turning while the wheel continues to turn. As the notch 75 passes under the tooth 74, the latter drops into place, and the unit is again ready'for use.

While I have shown and described in considerable detail two illustrative forms of my invention, it will be understood that various other changes may be made in the shape and arrangement of the several parts Without departing from the broad scope of the invention, as defined in the appended claim.

I claim:

A cable overload release device adapted to be serially connected into the operational control system of an artificial arm, comprising a casing attached to one side of said system, a wheel rotatably supported on said casing,

a cable attached to the other side of said system and wrapped around said wheel, a spring exerting a torque stops the plate with the notch 111 on the side opposite; 5

on said wheel tending to wind said cable thereon, a locking lever having a tooth engageable in a notch in said wheel to lock the latter against rotation, means actuated by excessive tension in said cable for disengaging said locking lever from said wheel to allow the latter to rotate and unwind cable therefrom, a flat interference ring between the side of said wheel and said casing in frictional engagement with said wheel and rotatable therewith by reason of frictional drag, the periphery of said ring being positioned to be engaged by said locking lever tooth to prevent said tooth entering said wheel notch, said ring having at one position of its periphery a notch which becomes positioned opposite said tooth in one position of said ring to permit said tooth to advance into engagement therein and into said notch in said wheel, coacting stops, one on said interference ring and one on said casing, for stopping said interference ring in said one position, wherein said ring notch is positioned opposite said tooth, during rotation of said ring with said wheel while said Wheel is turning in cable winding direction, said stops also stopping said ring in another position, wherein said ring notch is positioned away from said tooth, during rotation of said ring with said wheel while said wheel is turning in cable paying-out direction.

References Cited in the file of this patent UNITED STATES PATENTS 939,971 Brennan Nov. 16, 1909 1,184,069 Buck May 23, 1916 2,249,114 Cotfman July 15, 1941 

